Obesity is the cause of a myriad of serious health problems like the adult onset of diabetes and heart disease. In addition, the loss of weight is getting an obsession among an increasing proportion of the human population.
The causal relationship between hypercholesterolemia, particularly that associated with increased plasma concentrations of low density lipoproteins (hereinafter referred as LDL) and very low density lipoproteins (hereinafter referred as VLDL), and premature atherosclerosis and/or cardiovascular disease is now widely recognized. However, a limited number of drugs are presently available for the treatment of hyperlipidemia. Drugs primarily used for the management of hyperlipidemia include bile acid sequestrant resins such as cholestyramine and colestipol, fibric acid derivatives such as bezafibrate, clofibrate, fenofibrate, ciprofibrate and gemfibrozil, nicotinic acid and cholesterol synthesis inhibitors such as HMG Co-enzyme-A reductase inhibitors. The inconvenience of administration (a granular form to be dispersed in water or orange juice) and the major side-effects (gastrointestinal discomfort and constipation) of bile acid sequestrant resins constitute major drawbacks. Fibric acid derivatives induce a moderate decrease (by 5 to 25%) of LDL cholesterol (except in hypertriglyceridemic patients in whom initially low levels tend to increase) and, although usually well tolerated, suffer from side-effects including potentiation of warfarine, pruritus, fatigue, headache, insomnia, painful reversible myopathy and stiffness in large muscle groups, impotency and impaired renal function. Nicotinic acid is a potent lipid lowering agent resulting in a 15 to 40% decrease in LDL cholesterol (and even 45 to 60% when combined with a bile acid sequestrant resin) but with a high incidence of troublesome side-effects related to the drug's associated vasodilatory action, such as headache, flushing, palpitations, tachychardia and occasional syncopes, as well as other side-effects such as gastro-intestinal discomfort, hyperucemia and impairment of glucose tolerance. Among the family of HMG Co-enzyme-A reductase inhibitors, lovastatin and simvastatin are both inactive prodrugs containing a lactone ring which is hydrolyzed in the liver to form the corresponding active hydroxy-acid derivative. Inducing a reduction of LDL cholesterol by 35 to 45%, they are generally well tolerated with alow incidence of minor side effects. However there still remains a need for new lipid lowering agents with improved efficiency and/or acting via other mechanisms than the above mentioned drugs.
Plasma lipoproteins are water-soluble complexes of high molecular weight formed from lipids (cholesterol, triglyceride, phospholipids) and apolipoproteins. Five major classes of lipoproteins that differ in the proportion of lipids and the type of apolipoprotein, all having their origin in the liver and/or the intestine, have been defined according to their density (as measured by ultracentrifugation). They include LDL, VLDL, intermediate density lipoproteins (hereinafter referred as IDL), high density lipoproteins (hereinafter referred as HDL) and chylomicrons. Ten major human plasma apolipoproteins have been identified. VLDL, which is secreted by the liver and contains apolipoprotein B (hereinafter referred as Apo-B), undergoes degradation to LDL which transports 60 to 70% of the total serum cholesterol. Apo-B is also the main protein component of LDL. Increased LDL-cholesterol in serum, due to oversynthesis or decreased metabolism, is causally related to atherosclerosis. In contrast high density lipoproteins (hereinafter referred as HDL), which contain apolipoprotein A1, have a protective effect and are inversely correlated with the risk of a coronary heart disease. The HDL/LDL ratio is thus a convenient method of assessing the atherogenic potential of an individual's plasma lipid profile.
The two isoforms of apolipoprotein (apo) B, apo B-48 and apo B-100, are important proteins in human lipoprotein metabolism. Apo B-48, so named because it appears to be about 48% the size of apo B-100 on sodium dodecyl sulfate-polyacrylamide gels, is synthesized by the intestine in humans. Apo B-48 is necessary for the assembly of chylomicrons and therefore has an obligatory role in the intestinal absorption of dietary fats. Apo B-100, which is produced in the liver in humans, is required for the synthesis and secretion of VLDL. LDL, which contain about ⅔ of the cholesterol in human plasma, are metabolic products of VLDL. Apo B-100 is virtually the only protein component of LDL. Elevated concentrations of apo B-100 and LDL cholesterol in plasma are recognized risk factors for developing atherosclerotic coronary artery disease.
A large number of genetic and acquired diseases can result in hyperlipidemia. They can be classified into primary and secondary hyperlipidemic states. The most common causes of the secondary hyperlipidemias are diabetes mellitus, alcohol abuse, drugs, hypothyroidism, chronic renal failure, nephrotic syndrome, cholestasis and bulimia. Primary hyperlipidemias have also been classified into common hypercholesterolaemia, familial combined hyperlipidaemia, familial hypercholesterolaemia, remnant hyperlipidaemia, chylomicronaemia syndrome and familial hypertriglyceridaemia.
Microsomal triglyceride transfer protein (hereinafter referred as MTP) is known to catalyze the transport of triglyceride and cholesteryl ester by preference to phospholipids such as phosphatidylcholine. It was demonstrated by D. Sharp et al., Nature (1993) 365:65 that the defect causing abetalipoproteinemia is in the MTP gene. This indicates that MTP is required for the synthesis of Apo B-containing lipoproteins such as VLDL, the precursor to LDL. It therefore follows that an MTP inhibitor would inhibit the synthesis of VLDL and LDL, thereby lowering levels of VLDL, LDL, cholesterol and triglyceride in humans. MTP inhibitors have been reported in Canadian patent application No. 2,091,102 and in WO 96/26205. MTP inhibitors belonging to the class of polyarylcarboxamides have also been reported in U.S. Pat. No. 5,760,246 as well as in WO-96/40640 and WO-98/27979.
One of the goals of the present invention is to provide an improved treatment for patients suffering from obesity or atherosclerosis, especially coronary atherosclerosis and more generally from disorders which are related to atherosclerosis, such as ischaemic heart disease, peripheral vascular disease and cerebral vascular disease. Another goal of the present invention is to cause regression of atherosclerosis and inhibit its clinical consequences, particularly morbidity and mortality.